Neuroblastoma is a tumor of the peripheral nervous system that accounts for 15% of cancer-related deaths in children. Amplification and overexpression of the MYCN proto-oncogene occurs in 25% of neuroblastomas and is highly correlated with treatment failure and mortality. MYCN stimulates cell proliferation but paradoxically is a potent inducer of programmed cell death when its expression is uncoupled from survival signaling. To circumvent this safeguard against oncogene-driven neoplasia, cancer cells with deregulated MYC frequently exhibit defects in apoptotic pathways. We hypothesize that neuroblasts with MYCN amplification have obligate defects in pathways that engage or execute apoptosis, and these defects contribute to the malignant phenotype. We propose investigations into: (1) the mechanisms of MYCN-primed apoptosis under growth-limiting conditions or following genotoxic stress; (2) the mechanisms of escape from MYCN-primed apoptosis under these conditions; and (3) the use of novel agents to re-engage MYCN-primed apoptosis sensitivity both in vitro and in vivo. These studies will utilize a newly developed non-transformed human neuroectodermal cell line model (RPE1), neuroblastoma-derived cell lines and primary tumors, neuroblastomas arising in transgenic mice with targeted MYCN overexpression, and neuroblastoma xenografts. We will analyze the expression of apoptosis and survival genes in these model systems using microarray expression profiling complimented by traditional candidate gene approaches. Functional studies will be performed to identify and validate major death and survival pathways operative in neuroblastoma. Lastly, we will explore biological therapies that re-engage apoptosis sensitivity by inhibiting aberrant survival pathways, or de-repressing apoptosis-pathways inactivated in neuroblasts. Our goal is to use these studies to explore novel therapeutics that exploit the inherent apoptosis-priming function of deregulated MYCN for use in future clinical trials in neuroblastoma.